Art of treating ferrous metal articles



Patented Aug. 29, 1944 umrao ART OF TREATING FERROUS METAL ARTICLES David A. Russell and Stanley C. Kyle, Youngstown, Ohio Serial No. 440,096

No Drawing. Application April 22, 1942,

Claims.

Our invention relates to the coating of metals, and particularly to supplying ferrous metals with coatings devoid of oily or greasy constituents yet suitable for lubricating the metal during subsequent drawing or other cold working, such coatings moreover enhancing the subsequent resistance of the metal to corrosion.

More especially the invention, in certain of its aspects, is concerned with the provision of a slurry or wash, the principal ingredients of which are lime and water, possessing optimum capacity for adhering to a metal surface to aiford an improved lime coating thereon and to impart to the metal a marked degree of corrosion resistance, thereby to facilitate subsequent cold drawing and protect the metal from acid attack by neutralizing any acid present.

Other features eof the invention include the provision of novel metal-coating slurries v or washes in which instead of lime one of the principal ingredients may be an oxide or comparable compound, such as the acid, of some non-ferrous metal other than calcium, the specific properties of the wash varying in accordance with differences inthe properties of the metal compound used.

- It is thus a principal object of the invention to provide a novel wash for coating metals, especially ferrous metals, comprising compounds of other metals, which may be effectively used to lubricate the metal during subsequent wire drawthe following description of its practice proceeds with reference first to one method of preparing wirefor drawing to reduce its diameter and/or improve its surface finish.

It is a common practice in mills making iron and steel wire in quantity to initially hot roll rods from billets, then condition the rods and finally, in a plurality of operations, draw them into wire of the desired finished diameter. The conditioning just mentioned includes removing scale by pickling in dilute sulfuric acid, rinsing with water to remove excess acid, and then coating with lime by dipping in a hot lime bath a number of times depending upon specific existing conditions. The lime coating is then dried, or baked on if desired, before the wire is passed through the drawing dies, where the lime serves as a lubricant to facilitate the drawing operation, and the invention is especialy directed to the provision of a novel coating for use in place of the customary lime properties of our new slurry. is a capacity for adhering to ferrous metals with such tenacity that not only are fewer dips required to produce on the metal a lime coating of almost any de-. sired thickness, but the coating is of such inherent'physical strength that even when relatively thin it remains intact and substantially undamaged during subsequent handling. Our improved slurry moreover has certain other properties, apparently chemical as well as physical innature, but their precise character is not yet understood to the extent that it can be fully explained in exact terms. The effects of these properties have been observed, however, and include that of imparting to thesteel a remarkably enhanced-ability to resist atmospheric corrosion, an ability which is retained even after the coated metal has been drawn through wire drawing dies,

while the finish of the drawn wire is exceptionally bright and smooth.

The wire is also appreciably more effectively preserved against rust or corrosion following subsequent application of anti-rust or slushing oils when it has been treated in accordance with our method prior to final drawing-and we therefore attain not only economic advantages through reduction of the number of dips required and greater tenacity of the resulting coating, but provide a. procedure which produces wire having unique and improved inherent properties itself as compared with wire produced in accordance with prior methods.

' The introduction of the mono-sodium phosphate into the slurry may be effected in the liming tank or elsewhere either while the slurry is being initially.made up or after the. lime and water have been mixed together in the desired proportions to produce it, and whether the phosphate is introduced in solid form or as a solu-' tion appears to make little if any difference in the result.

While as above suggested we have been unable to determine the precise chemical reactions entering into the practice of our invention, it is our present belief that the mono-sodium phosphate may react at least in part with the lime in the slurry to produce greater or less quantities of one or more of .the double phosphates of calcium and sodium and/or that these, and/or the mono-sodium phosphate itself, may act physically after the manner of certain colloids in giving rise to polar groups which produce the effect of a bonding agent. This latter effect, if in fact it is produced, perhaps accounts for the enhanced adherence of the coating to the steel.

We have also observed that the breakdown of drawing greases is inhibited when they are used in drawing wire treated in accordance with the method, thus avoiding creation of the corrosive compounds which often result therefrom and become imbedded in the metal surface to promote later corrosion.

Moreover, by the use of mono-sodium phosphate with compounds of other non-ferrous metals we attain still further advantages, especially from the standpoints of corrosion resistance, hardening, toughening, etc., andthese are.

to some extent dependent upon the identity of the specific metal compound employed.

Thus, when mono-sodium phosphate is added to a true water solution of either chromic oxide (chromic acid, H2CIO4) or molybdic oxide (molybdic acid, H2MOO4) a colloid is formed and when steel is coated with it and then dried and heated in a reducing atmosphere it takes up the While we have thus referred to certain specific metallic compounds as suitable'for the purposes of the invention with special mention of oxides of chromium, molybdenum and aluminum in addition to lime, the insoluble oxides of magnesium,

barium, silicon, titanium, lead, tin and manganese may be caused to adhere to steel surfaces by the use of mono-sodium phosphate in washes containing them.

Furthermore, while we have as noted given specific examples of the practice of our invention and have mentioned certain of the results we attain thereby, it will be understood that changes and modifications in the performance of the actual operations as well as in the specific nature and proportions of the ingredients or materials used will readily occur to those skilled in the art and may be made if desired Wit out departing from the spirit and scope of the invention as defined in the appended claims.

Having thus described our invention, we claim and desire to protect by Letters Patent of the United States:

1. A method of treating steel preparatory to cold working Which comprises the steps of immersin it in a slurry. consisting of a colloidal suspension cf lime and mono-sodium phosphate in water, removing it from the slurry and permitting the adherent slurry to dry at least in part thereon.

2. The method of treating steel which comprises subjecting it to'the deposition of a wash consisting of a colloidal suspension in water of a metal oxide and an amount of mono-sodium phosphate equivalent in weight to about 1% of that of the oxide.

' 3. The method of imparting corrosion resistance to the surface of a steel article which comprises forming on the article a coating by immersion in a colloidal suspension derived from mixing calcium oxide and mono-sodium phosphate.

4. A colloidal type suspension for treating ferrous metal articles consisting of about 100 parts of lime and 1 part of mono-sodium phosphate by weight in water.

5. A wash for treating ferrous metal articles which consists of a substantially colloidal suspension in water resulting from the action of mono-sodium phosp-hateon lime.

DAVID A. RUSSELL. STANLEY C; KYLE. 

